To have clear vision the eye must be stabilized in space despite movements of the head and visual surround. The optokinetic system uses the movement of the visual world on the retina, retinal slip, as a signal to induce stabilizing eye movements, such as optokinetic nystagmus. The aim of this investigation is to study the neural structures, particularly the visual input, involved in this system. We propose first to identify the brain nuclei and retinal structures that respond to retinal slip and then to study the cytology of these structures. A preliminary study using 2-deoxy-glucose (2DG) to map brain areas that become metabolically active during retinal slip implied that the visual input arrives through the accessory optic system (AOS) and the pretectal nuclei. These studies demonstrated that the nucleus of the basal optic root of the AOS is activated during slow vertical retinal slip and the lentiform nucleus of the mesencephalon, a pretectal nucleus, is activated during horizontal movement and both are activated during torsional movement. Using the 2DG method we propose: (1) to extend these studies in an effort to confirm these results and to identify other brain nuclei involved in this system, (2) to identify retinal structures that respond to retinal slip, and (3) to determine whether the sites to which the retinal structures project are topographically organized. The second phase of the study will involve cytological characterization of the functional areas identified in the first phase. Golgi impregnation methods will be used to identify and characterize the neuronal cell types present. Electron microscopic methods will reveal synaptic linkages within each nucleus, and deafferentation studies will demonstrate the source of the synaptic terminals. This study in combination with electrophysiological and behavioral studies of this system may permit a better understanding of the disorders such as congenital nystagmus as well as other deficits in oculomotor stabilization.